Multi-band mobile antenna loading coil



Oct. 4, 1955 E 1 2,719,920

MULTI-BAND MOBILE ANTENNA LOADING COIL Filed March 20, 1951 0 W1 W 57x95 ummmommumummommmmommmn I w T 30 IN VEN TOR.

ATTD R N EYE United States Patent MULTI-BAND MOBILE ANTENNA LOADING COIL Glenn R. Ellis, Bay City, Tex. Application March 20, 1951, Serial No. 216,485 2 Claims. Cl. 250-33 This invention relates to radio communication equipment, and more particularly to a multi-band antenna loading coil.

The object of the invention is to provide a multi-band mobile antenna loading coil for use on mobile radio communication equipment, whereby the antenna or radiator system can be resonated to several widely separated frequencies with only one loading coil.

Another object of the invention is to provide a multiband mobile antenna loading coil whereby only one loading coil is required in order to cover several widely separated operating frequencies, the apparatus of the present invention being provided with rugged, positive, low-loss switching contacts, the coil operating at high efliciency, and whereby losses due to long leads from desired turns and shorting switches are eliminated, and whereby critical tuning adjustments can be obtained.

A further object of the invention is to provide a multiband mobile antenna loading coil which is extremely simple and inexpensive to manufacture.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawings forming a part of this application and in which like numerals are used to designate like parts throughout the same:

Figure 1 is a longitudinal sectional view taken through the loading coil constructed according to the present invention;

Figure 2 is a sectional view taken on the line 2-2 of Figure 1;

Figure 3 is a sectional view taken on the line 3--3 of Figure 1;

Figure 4 is a sectional view taken on the line 44 of Figure 1;

Figure 5 is a diagrammatic view showing the circuit diagram that corresponds to the structure of Figure 1.

Referring in detail to the drawings, the numeral designates a hollow, elongated support member which is tubular and which may be fabricated of a suitable insulating material, such as Bakelite. Wound around the exterior of the support member 10 is a coil form or wire 11, Figure 1, and a metal end piece 12 serves to close the lower end of the support member 10.

Mounted in the upper end of the support member 10 is a metal end piece 14. Mounted for adjustable or sliding movement through the support member 10 is a vertical antenna or radiator 15, and a banana plug 16 is mounted on an end of the antenna 15. Projecting from the end piece 14 or secured thereto is a split sleeve 18, the splits in the sleeve 18 being indicated by the numeral 19, Figure 2. A portion of the split sleeve 18 is threaded exteriorly, as at 20, and arranged in threaded engagement with the threaded portion 20 is a knurled lock nut 17. By tightening the lock nut 17, the antenna or radiator 15 can be locked or maintained immobile in any of its adjusted positions.

It will be seen that the end piece 14 and its sleeve 18 are both provided with a bore for slidably receiving there- 2,719,920 Patented Oct. 4, 1955 in the antenna 15 and the lower portion of the end piece 14 is cut away to provide a central socket 21 which provides a snug fit for the heavy duty banana type plug 16 which is attached to the end of the radiator 15.

The end piece 14 is secured to the support member 10 by means of a screw 22, Figures 1 and 3, and a screw 23 which has a head thereon provides an electrical contact between the wire coil 11 and the end piece 14. Similarly, a screw 24 serves to hold the end piece 12 connected to the support member 10, while a headed screw 25 provides an electrical contact between the wire coil and the end piece 12. The spacing, size of the wire and number of turns in the coil form 11 are determined by the desired band of operating frequencies.

Arranged within the support member 10 is a plurality of shorting jacks which are each indicated by the numeral 26. Each of the shorting jacks 26 includes a disc portion 27 which snugly engages the interior surface of the support member 10, and formed integrally with the disc 27, or secured thereto, is a transverse, hollow collar 28 which has passing slidably therethrough the antenna 15. The shorting jacks26 are made of a suitable conducting material, such as metal, and the banana plug 16, when seated in one of the collars 28, will short circuit the winding coil 11. Screws 29 serve to hold the shorting jacks 26 in place within the support member 10, and the screws 29 also provide an electrical contact with the desired turn of wire on the loading coil. The heads or outer ends of the screws 29 may be soldered to the wire 11 in order to insure electrical contact with the wire.

The metal end piece 12 is provided with a shank 30 which has a diameter of sufiicient size to fit any conventional flexible mobile antenna mount. However, if center loading of the antenna is desired, the shank 30 may be fitted into a section of the antenna above the flexible mobile antenna mount.

From the foregoing it is apparent that a multi-band mobile antenna loading coil has been provided, wherein the antenna or radiation system of mobile radio communication equipment can be resonated to several widely separated frequencies with only one loading coil. The operation of the apparatus is as follows: With the antenna or radiator 15 drawn out of the coil until the plug 16 engages end piece 14, the antenna system will be resonated at the lowest frequency for which it is designed. By pushing the antenna 15 into the coil so that the plug 16 engages the uppermost shorting jack 26, the section of turns of the loading coil between the screw 29 and end piece 14 will be short circuited leaving as active turns the section between the shorting jack 27 and the end piece 12. Since the number of active turns in the loading coil are now less than the total number of turns, the antenna system will be resonant at a higher frequency than before. Similarly, by moving the antenna 15 so that the banana plug 16 engages in the intermediate shorting jack 26, or the lowermost shorting jack 26, the antenna system will resonate at still higher frequencies. The antenna 15 may be pushed all the way into the coil so that the plug 16 engages the socket 31 in end piece 12 to thereby short circuit the entire loading coil. This is the highest frequency at which the antenna system will resonate. This permits five widely separated operating frequencies with only one loading coil. Thus, there has been provided a method of using the antenna or radiator itself as the shorting switch.

The advantages of the apparatus of the present invention are that only one loading coil is required to cover several widely separated operating frequencies, and positive rugged low-loss switching contacts are provided. Also, there will be greater efiiciency and an elimination of losses due to long leads from desired turns and shorting switch. Further, there will be more radiated power,

and the loading coil is in free space as is the antenna, and critical tuning adjustments can be obtained, since the long plug and jack permit adjusting the physical length of the radiator without disengaging the plug from the jack.

What is claimed is:

1. In a loading coil, a support member, a first end piece mounted in one end of said support member, a second end piece mounted in the other end of said support member, a coil winding wound around said support member, a plurality of spaced shorting jacks arranged in said support member, antenna slidably arranged in said second end piece and having a plug therein for movement into and out of engagement with said shorting jacks, said support member being tubular in shape and fabricated of an insulated material, a split sleeve projecting from said second end piece, a lock nut arranged in threaded engagement with said sleeve for preventing accidental movement of said antenna, and screws providing electrical contact between the coil winding and the end pieces and shorting jacks.

2. In a loading coil, a support member, a first end piece mounted in one end of said support member, a

second end piece mounted in the other end of said support member, a coil winding wound around said support member, a plurality of shorting jacks arranged in said support member, an antenna slidably arranged in said second end piece and having a plug therein for movement into and out of engagement with said shorting jacks, a sleeve projecting from said second end piece, a lock nut arranged in threaded engagement with said sleeve for preventing accidental movement of said antenna, and screws providing electrical contact between the coil winding and the end pieces and shorting jacks.

References Cited in the file of this patent UNITED STATES PATENTS 1,450,038 Hill Mar. 27, 1923 1,497,411 Snell June 10, 1924 1,768,666 Conrad July 1, 1930 1,971,872 OBrien Aug. 28, 1934 2,495,579 Ferris et al. Jan. 24, 1950 2,558,487 Hills June 26, 1951 

